Dihydroxy diaryl alkenes



United States Patent DIHYDROXY DIARYL ALKENES David J. Beaver, Richmond Heights, Mo., and Richard 0. Zerbe, Nitro, W. Va., assignors 'to Monsanto Chemical Company, St. Louis, Mo., a corporation of Delaware No Drawing. Original application October 26, 1951, Serial No. 253,474. Divided and this application December 16, 1957, Serial No. 702,770

Claims. (Cl. 260-619) This invention relates to a new and novel family of dihydroxy diaryl alkenes. More particularly it relates to dihydroxy diaryl alkenes derived by condensing unsaturated aldehydes with disubstituted phenols containing a polycarbon alkyl group in the 2-position and an alkyl group in the 5-position and to their method of manufacture. I

The new compounds may be represented by the general formula where R is an alkenyl group, R is a polycarbon alkyl group of at least four carbon atoms and R is a lower alkyl group.

Dialkyl phenols suitable as starting materials for the preparation of the new compounds may be prepared by a variety of methods, however the position of the alkyl groups exerts a profound influence on the antioxidant properties and it is essential to employ phenols having the proper orientation of the alkyl groups. Exemplary of one suitable class of dialkyl phenols are the products prepared by alkylating a meta or 3-alkyl substituted phenol with a tertiary alcohol or olefin in the presence of sulfuric acid or phosphoric acid catalyst. This aflords a convenient direct synthesis and the published evidence indicates that under these conditions the alkyl group enters the 6position. In any event this class of products have proven to be satisfactory. Other methods of synthesis are equally well known and available for the introduction of normal alkyl groups. Examples of suitable dialkyl phenols together with their physical properties are listed below:

6-tert. butyl m-cresol, B.P. 130 C./20 mm.

Z-tert. butyl S-ethyl phenol, B.P. 135-438 C./20 mm. 6-tert. amyl m-cresol, B.P. 133137 C./20 mm. 6-n-buty1 m-cresol, B.P. 134 C./l5 mm. 2-n-butyl S-ethyl phenol, B.P. 119-121" C./4 mm. 6-isoamyl m-cresol, B.P. 104-106 C./2 mm. 6-n-hexyl m-cresol, B.P. 118l19 C./2.5 mm. 6-isohexyl m-cresol, B.P. 108-109 C./ 1.5 mm. 6-n-heptyl m-cresol, B.P. l26-128 C./2.5 mm. 6-n-octyl m-cresol, B.P. 141-143" C./ 3 mm.

6-n-decyl m-cresol, B.P. 146-147 C./2 mm. 6-n-dodecyl m-cresol, B.P. 183 C./ 3 mm. (M.P. 44 C.)

Still further examples of suitable 2,5-dialkyl phenols are 6-sec. butyl m-cresol, 6-(2,4-dimethyl butyl) m-cresol, 6-sec. amyl m-cresol, 6-sec. octyl m-cresol and 2,5-di-tert. butyl phenol.

Among the aldehydes which may be employed are crotonaldehyde, fI-ethyl-a-methyl acrolein, u-ethyl-fi-propyl acrolein and the like.

The condensation of the phenol and the aldehyde is 2,919,294 Patented Dec. 29, 1959 usually carried out in a molar proportion of 2:1 in the presence of an acidic condensation catalyst, as for example, hydrochloric acid. Where desired solvents and/ or dispersing mediums may be employed although the reactions are actually carried out in the absence of either.

The following crystalline compounds were prepared by refluxing a half gram mole of the appropriate phenol and one-fourth gram mole of the aldehyde in the presence of 4.7 grams of concentrated hydrochloric acid. The mixtures were refluxed at 95 C. The reaction times varied, these being determined by spot testing at intervals with a solvent or precipitant consisting chiefly of heptanes and quenching the reaction when crystal formation was observed and before suflicient resin had formed to interfere with purification of the crystals. The reaction mixture was cooled and thereto was added 100 ml. of the liquid aliphatic hydrocarbon consisting chiefly of heptanes. The mass was agitated for 4 hours at 30-32 C. and the white solid filtered ofi, washed with several portions of the aforesaid hydrocarbon and subsequently dried.

1) 4,4-(2-ethyl-2-hexene.-l-ylidene) -bis(.6-tert. butyl m-cresol), M.P. 210.2210.6 C. (corn), recrystallized from heptane, white solid, from 2-ethyl-2-hexenal and 6-tert. butyl m-cresol, reaction time 3 hours. Carbon found 82.46%, calc. 82.46%. Hydrogen found 9.89%, calc. 10.16%.

(2) 4,4'-(2-methyl-2-pentene-l-ylidene) bis (6-tert. butyl m-cresol), white solid, M.P. 190.1-190.5 C., recrystallized from heptane, from Z-methyl Z-pentenal and 6-tert. butyl m-cresol, reaction time 18 hours. Carbon found 82.15%, calc. 82.30%. Hydrogen found 9.52%, calc. 9.87%.

As illustrative of the antioxidant properties of the new dihydroxy diarylalkenes, rubber stocks were compounded comprising Parts by weight To each base stock was added 1.0 part by weight of one of the antioxidants listed below. The respective stocks were cured in the usual manner by heating in a press at 126 C. for 45 and minutes. The first column of data in the following table shows the percent retention of ultimate tensile strength obtained after aging for 12 hours in an air bomb at 121 C. at 80 lbs./in. The figures are the averages for the two cures. The second column shows the resistance to discoloration. Samples of the cured stocks were, exposed under an S-1 sunlamp for 10 days. After exposure the light reflected from the surface of the stocks was measured by means of a Photovolt refiectance meter calibrated against reflectance of standard MgO as The data shown are percent reflectance of the 60 minute cures.

Ilia R2 H HO -O OH R R1 R;

where R is an alkenyl group containing at least three but not more than seven carbon'atoms the unsaturation consisting in one vdouble bond, R is an alkyl group of 4-12 carbon atoms and R is a lower alkyl group.

2. The method of making a dihydroxy diaryl alkene which comprises heating at about 95 C. in the presence of an acidic condensation catalyst an aldehyde of the structure RCHO where R is an acyclic unsaturated hydrocarbon radical in which the unsaturation consists in one double bond and which acyclic radical contains at least three but not more than seven carbon atoms and a phenol of the structure where R is an alkyl group of 4-12 carbonatoms, R is a lower alkyl group, with the elimination of Water as a byproduct of the condensation and terminating the reaction before resinous polymers are produced.

3. As a composition of matter a compound of the structure where R is an acyclic unsaturated hydrocarbon radical in which the unsaturation consists in one double bond and which acyclic radical contains at least three but not'more than seven carbon atoms.

4. As a composition of matter a compound of the structure 5. As a composition of matter a compound of th structure References Cited in the file of this patent Niederl et al.: 63 Jour. Amer. Chem. Soc., 1731-1733 (1941). 

1. AS A COMPOSITION OF MATTER A COMPOUND OF THE STRUCTURE 